Post passivation interconnection schemes on top of IC chips

ABSTRACT

A new method is provided for the creation of interconnect lines. Fine line interconnects are provided in a first layer of dielectric overlying semiconductor circuits that have been created in or on the surface of a substrate. A layer of passivation is deposited over the layer of dielectric, a thick second layer of dielectric is created over the surface of the layer of passivation. Thick and wide interconnect lines are created in the thick second layer of dielectric. The first layer of dielectric may also be eliminated, creating the wide thick interconnect network on the surface of the layer of passivation that has been deposited over the surface of a substrate.

This application is a continuation of application Ser. No. 11/273,071,filed on Nov. 14, 2005, now U.S. Pat. No. 7,405,150, which is acontinuation of application Ser. No. 10/653,628, filed on Sep. 2, 2003now U.S. Pat. No. 7,443,033, which is a continuation of application Ser.No. 10/278,106, filed on Oct. 22, 2002, now U.S. Pat. No. 6,734,563,which is a division of application Ser. No. 09/691,497, filed on Oct.18, 2000, now U.S. Pat. No. 6,495,442.

RELATED PATENT APPLICATIONS

This application is related to U.S. Ser. No. 09/251,183, filed on Feb.17, 1999, now U.S. Pat. No. 6,383,916, which is a continuation-in-partof U.S. Ser. No. 09/216,791, filed on Dec. 21, 1998, now abandoned. Thisapplication is also related to U.S. Ser. No. 09/637,926, filed on Aug.14, 2000, now abandoned.

BACKGROUND OF THE INVENTION

(1.) Field of the Invention

The invention relates to the fabrication of integrated circuit devices,and more particularly, to a method of post-passivation processing forthe creation of conductive interconnects.

(2.) Description of the Prior Art

Improvements in semiconductor device performance are typically obtainedby scaling down the geometric dimensions of the Integrated Circuits;this results in a decrease in the cost per die while at the same timesome aspects of semiconductor device performance are improved. The metalconnections which connect the Integrated Circuit to other circuit orsystem components become of relative more importance and have, with thefurther miniaturization of the IC, an increasingly negative impact onthe circuit-performance. The parasitic capacitance and resistance of themetal interconnections increase, which degrades the chip performancesignificantly. Of most concern in this respect is the voltage drop alongthe power and ground buses and the RC delay of the critical signalpaths. Attempts to reduce the resistance by using wider metal linesresult in higher capacitance of these wires.

To solve this problem, one approach has been to develop low resistancemetal (such as copper) for the wires while low dielectric materials areused in between signal lines. Current practice is to create metalinterconnection networks under a layer of passivation, this approachhowever limits the interconnect network to fine line interconnects,associated with parasitic capacitance and high line resistivity. Thelatter two parameters, because of their relatively high values, degradedevice performance, resulting in even more severe effects for higherfrequency applications and for long interconnect lines that are, forinstance, used for clock distribution lines. Also, fine lineinterconnect metal cannot carry high values of current that is typicallyneeded for ground busses and for power busses.

It has previously been stated that it is of interest to thesemiconductor art to provide a method of creating interconnect linesthat removes typical limitations that are imposed on the interconnectwires, such as unwanted parasitic capacitances and high interconnectline resistivity. The invention provides such a method. An analogy canbe drawn in this respect whereby the currently (prior art) usedfine-line interconnection schemes, which are created under a layer ofpassivation, are the streets in a city; in the post-passivationinterconnection scheme of the present invention, the interconnectionsthat are created above a layer of passivation can be considered thefreeways between cities.

FIG. 1 shows a cross section of a silicon substrate on the surface ofwhich has been created a conductive interconnect network. The structurethat is shown in cross section in FIG. 1 addresses only and is limitedto prior art power and ground distribution networks. The variousfeatures that have been highlighted in FIG. 1 are the following:

40, a silicon substrate on the surface of which has been created aninterconnect network

42, a sample number of semiconductor circuits that have been created inor on the surface of the substrate 40

44, two electrostatic discharge (ESD) circuits created in or on thesurface of the substrate 40; one ESD circuit is provided for each pinthat is accessible for external connections (pins 52, see below)

46 is a layer in which interconnect lines are provided; theseinterconnect lines are above the surface of substrate 40 and under thelayer 48 of passivation and represent a typical application of prior artfine-line interconnects; these fine-line interconnects in layer 46typically have high resistivity and high parasitic capacitance

48 is a layer of passivation that is deposited over the surface of thelayer 46 in which interconnect lines are provided

50 is a power or ground bus that connects to the circuits 42 viafine-line interconnect lines provided in layer 46; this power or groundbus 50 is typically of wider metal since this power or ground buscarries the accumulated current or ground connection for the devices 42

52 is a power or ground pin that passes through the layer 48 ofpassivation and that has been connected to the power or ground bus 50.

From the above the following can be summarized: circuits 42 and 44 arecreated in or on the surface of a silicon substrate 40, interconnectlines in layer 46 are created for these circuits 42 and 44 for furtherinterconnection to external circuitry, the circuits 42 and 44 are, on aper I/O pin basis, provided with an ESD circuit 44, these circuits 42together with the ESD circuit 44 are connected to a power or ground pin52 that penetrates a layer 48 of passivation. The layer 48 ofpassivation is the final layer that overlies the created interconnectline structure, and the interconnect lines underneath the layer 48 ofpassivation are fine line interconnects and have all the electricaldisadvantages of fine line interconnects such as high resistivity andhigh parasitic capacitance.

Relating to the cross section that is shown in FIG. 1, the followingcomments applies: ESD circuits 44 are, as is known-in the art, providedfor the protection of semiconductor circuits 42 against unexpectedelectrical charges. For this reason, each pin that connects to asemiconductor circuit 42 must be provided with an ESD circuit 44.

FIG. 2 shows a cross section of a prior art configuration that resemblesthe cross section shown in FIG. 1. The structure that is shown in crosssection in FIG. 2 however addresses only and is limited to clock andsignal distribution networks. FIG. 2 shows in addition (to thepreviously highlighted aspects of FIG. 1):

45 are two ESD circuits that are provided in or on the surface of thesubstrate 40; ESD circuits 45 are always required for any externalconnection to an input/output (I/O) pin 56

45′ which are circuits that can be receiver or driver or I/O circuitsfor input (receiver) or output (driver) or I/O purposes respectively

54 is a clock bus

56 is a clock or signal pin that has been extended through the layer 48of passivation.

The same comments apply to the cross section that is shown in FIG. 2 aspreviously have been made with respect to FIG. 1, with as a summarystatement that the layer 48 of passivation is the final layer thatoverlies the created structure, and the interconnect lines in layer 46underneath the layer 48 of passivation are fine line interconnects andhave all the electrical disadvantages of fine line interconnects such ashigh resistivity and high parasitic capacitance.

Further applies to the cross section that is shown in FIG. 2, where pins56 are signal or clock pins:

pins 56 must be connected to ESD circuits 45 and driver/receiver or I/Ocircuits 45′

for signal or clock pins 56, these pins 56 must be connected not only toESD circuits 45 but also to driver or receiver or I/O circuits,highlighted as circuits 45′ in FIG. 2

after (clock and signal) stimuli have passed through the ESD circuits 45and driver/receiver or I/O circuits 45′, these stimuli are furtherrouted using, under prior art methods, fine-line interconnect wires inlayer 46. A layer 48 of passivation is deposited over the dielectriclayer 46 in which the interconnect network has been created.

It is therefore of interest to the semiconductor art to provide a methodof creating interconnect lines that removes typical limitations that areimposed on the interconnect wires, such as unwanted parasiticcapacitances and high interconnect line resistivity.

SUMMARY OF THE INVENTION

A principal objective of the invention is to provide a method for thecreation of interconnect metal that allows for the use of thick and widemetal.

Another objective of the invention is to provide a method for thecreation of interconnect metal that uses the application of thick layerof dielectric such as polymer.

Yet another objective of the invention is to provide a method thatallows for the creation of long interconnect lines, whereby these longinterconnect lines do not have high resistance or introduce highparasitic capacitance.

A still further objective of the invention is to create interconnectlines that can carry high values of current for the creation of powerand ground distribution networks.

A still further objective of the invention is to create interconnectmetal that can be created using cost effective methods by creating theinterconnect metal over a layer of passivation after the layer ofpassivation has been deposited.

In accordance with the objectives of the invention a new method isprovided for the creation of interconnect lines. Fine line interconnectsare provided in a first layer of dielectric overlying semiconductorcircuits that have been created in or on the surface of a substrate. Alayer of passivation is deposited over the layer of dielectric; a thicksecond layer of dielectric is created over the surface of the layer ofpassivation. Thick and wide interconnect lines are created in the thicksecond layer of dielectric.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section of a silicon substrate over which a prior artfine-line interconnect network is created over which a layer ofpassivation is deposited; power and/or ground pins are provided throughthe layer of passivation for external connection. The structure that isshown in cross section in FIG. 1 addresses only and is limited to priorart power and ground distribution networks.

FIG. 2 is a cross section of a silicon substrate over which a prior artfine-line interconnect network is created over which a layer ofpassivation is deposited; clock and/or signal pins are provided throughthe layer of passivation for external connection. The structure that isshown in cross section in FIG. 2 addresses only and is limited to priorart clock and signal distribution networks.

FIG. 3 a is a cross section of a silicon substrate over which aninterconnect network is created according to the invention. Power and/orground pins are provided through the layer of passivation for externalconnection. The structure that is shown in cross section in FIGS. 3 aand 3 b addresses only and is limited to power and ground distributionnetworks of the invention.

FIG. 3 b shows power and ground distribution lines that are below alayer of passivation and power and ground distribution lines that areabove a layer of passivation.

FIG. 4 a is a cross section of a silicon substrate over which aninterconnect network is created according to the invention. An ESDand/or driver and/or receiver circuit access pin is provided through thelayer of dielectric for external connection. The structure that is shownin cross section in FIGS. 4 a and 4 b addresses only and is limited toclock and signal distribution networks of the invention.

FIG. 4 b shows clock and signal distribution lines that are below alayer of passivation and clock and signal distribution lines that areabove a layer of passivation.

FIG. 5 a is a cross section of a silicon substrate over which aninterconnect network is created according to the invention. No I/Oconnect pin is provided through the layer of dielectric for externalconnection. The structure that is shown in cross section in FIGS. 4 aand 4 b addresses only and is limited to clock and signal distributionnetworks of the invention.

FIG. 5 b shows clock and signal distribution lines that are below alayer of passivation and clock and signal distribution lines that areabove a layer of passivation.

FIG. 6 shows a cross section of the interconnection scheme of thereferenced application invention.

FIG. 7 a shows a cross section of a simplified version of the substrateand the layers that are created on the surface of the substrate underthe processes of the referenced application.

FIG. 7 b shows an inductor has been added above the layer ofpassivation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For purposes of reference and for clarity of understanding, FIG. 6 istaken from related U.S. application Ser. No. 09/251,183 and is hereinincorporated by reference.

Referring now more specifically to FIG. 6, there is shown a crosssection of one implementation of the referenced application. The surfaceof silicon substrate 10 has been provided with transistors and otherdevices (not shown in FIG. 6). The surface of substrate 10 is covered bya dielectric layer 12, layer 12 of dielectric is therefore depositedover the devices that have been provided in the surface of the substrateand over the substrate 10. Conductive interconnect lines 11 are providedinside layer 12 that connect to the semiconductor devices that have beenprovided in the surface of substrate 10.

Layers 14 (two examples are shown) represent all of the metal layers anddielectric layers that are typically created on top of the dielectriclayer 12. Layers 14 that are shown in FIG. 6 may therefore containmultiple layers of dielectric or insulation and the like, conductiveinterconnect lines 13 made up of the network of electrical connectionsthat are created throughout layers 14. Overlying and on the surface oflayers 14 are points 16 of electrical contact. These points 16 ofelectrical contact can for instance be bond pads that establish theelectrical interconnects to the transistors and other devices that havebeen provided in the surface of the substrate 10. These points ofcontact 16 are points of interconnect within the IC arrangement thatneed to be further connected to surrounding circuitry. A passivationlayer 18, formed of for example silicon nitride, is deposited over thesurface of layer 14 to protect underlying layers from moisture,contamination, etc.

The key steps of the above referenced application begin with thedeposition of a thick layer 20 of polyimide that is deposited over thesurface of layer 18. Access must be provided to points of electricalcontact 16, for this reason a pattern of openings 22, 36 and 38 isetched through the polyimide layer 20 and the passivation layer 18. Thepattern of openings 22, 36 and 38 aligns with the pattern of electricalcontact points 16. Contact points 16 are, by means of the openings22/36/38 that are created in the layer 20 of polyimide, electricallyextended to the surface of layer 20.

The above referenced material that is used for the deposition of layer20 is polyimide; the material that can be used for this layer is notlimited to polyimide but can contain any of the known polymers(SiCl_(x)O_(y)). The indicated polyimide is the preferred material to beused for the processes of the invention for the thick layer 20 ofpolymer. Examples of polymers that can be used are silicons, carbons,fluoride, chlorides, oxygens, silicone elastomer, parylene or teflon,polycarbonate (PC), polysterene (PS), polyoxide (PO), poly polooxide(PPO), benzocyclobutene (BCB).

Electrical contact contacting with the contact points 16 can now beestablished by filling the openings 22/36/38 with a conductive material.The top surfaces 24 of these metal conductors that are contained inopenings 22/36/38 can now be used for connection of the IC to itsenvironment, and for further integration into the surrounding electricalcircuitry. The semiconductor devices that have been provided in thesurface of substrate 10 can, via the conductive interconnects containedin openings 22/36/38, be further connected to surrounding components andcircuitry. Interconnect pads 26 and 28 are formed on top of surfaces 24of the metal interconnects contained in openings 22, 36 and 38. Thesepads 26 and 28 can be of any design in width and thickness toaccommodate specific circuit design requirements. A pad 26 or 28 can,for instance, be used as a flip chip pad. Other pads 26 or 28 can beused for power distribution or as a ground or signal bus. The followingconnections can, for instance, be made to the pads shown in FIG. 6: pad26 can serve as a flip chip pad, and pad 28 can serve as a flip chip pador can be connected to electrical power or to electrical ground or to anelectrical signal bus. Pad size and the standard rules and restrictionsof electrical circuit design determine the electrical connections towhich a given pad 26 or 28 lends itself.

The following comments relate to the size and the number of the contactpoints 16, as shown in FIG. 6. Because these contact points 16 arelocated on top of a thin dielectric (layer 14, FIG. 6) the pad sizecannot be too large since a large pad size brings the circuits a largecapacitance. In addition, a large pad size will interfere with therouting capability of that layer of metal. It is therefore preferred tokeep the size of the pad 16 relatively small. The size of pad 16 ishowever also directly related with the aspect ratio of vias 22/36/38. Anaspect ratio of about 5 is acceptable for the consideration of viaetching and via filling. Based on these considerations, the size of thecontact pad 16 can be in the order of 0.5 μm to 30 μm, the exact sizebeing dependent on the thickness of layers 18 and 20.

For higher aspect ratio vias, the vias are filled with via plugs beforethe deposition of the metal layers 26 and 28. However, for vias thathave lower aspect ratios (for example less than 2), the via plugs maynot be needed in which case the metal of layers 26 and 28 can directlyestablish contact with the pads 16.

The referenced application does not impose a limitation on the number ofcontact pads that can be included in the design, this number is not onlydependent on package design requirements but is mostly dependent on theinternal circuit design requirements. Layer 18 in FIG. 6 can be atypical IC passivation layer.

The most frequently used passivation layer in the present state of theart is plasma enhanced CVD (PECVD) oxide and nitride. In creating layer18 of passivation, a layer of approximately 0.5 μm PECVD oxide can bedeposited first followed by a layer of approximately 0.7 μm nitride.Passivation layer 18 is very important because it protects the devicewafer from moisture and foreign ion contamination. The positioning ofthis layer between the sub-micron process (of the integrated circuit)and the tens-micron process (of the interconnecting metallizationstructure) is of critical importance since it allows for a cheaperprocess that possibly has less stringent clean room requirements for theprocess of creating the interconnecting metallization structure.

Layer 20 is a thick polymer dielectric layer (for example polyimide)that has a thickness in excess of 2 μm (after curing). The range of thepolymer thickness can vary from 2 μm to 150 μm, dependent on electricaldesign requirements.

For the deposition of layer 20 the Hitachi-Dupont polyimide HD 2732 or2734 can, for example, be used. The polyimide layer 20 can be spin-oncoated and cured. After spin-on coating, the polyimide layer 20 will becured at 400 degrees C. for 1 hour in a vacuum or nitrogen ambient. Forthicker polyimide film 20, the polyimide film 20 can be multiple coatedand cured.

Another material that can be used to create layer 20 is the polymerbenzocyclobutene (BCB). This polymer is at this time commerciallyproduced by for instance Dow Chemical and has recently gained acceptanceto be used instead of typical polyimide application.

The dimensions of openings 22, 36 and 38 have previously been discussed.The dimension of the opening together with the dielectric thicknessdetermines the aspect ratio of the opening. The aspect ratio challengesthe via etch process and the metal filling capability. This leads to adiameter for openings 22/36/38 in the range of from approximately 0.5 μmto 30 μm. The height for openings 22/36/38 can be in the range ofapproximately 2 μm to 150 μm. The aspect ratio of openings 22/36/38 isdesigned such that filling of the via with metal can be accomplished.The via can be filled with CVD metal such as CVD tungsten or CVD copper,with electro-less nickel, with a damascene metal filling process, withelectroplating copper, etc. As previously stated, for low aspect ratiovias, the filling of the vias is not required as an extra processingstep. A direct contact can be established between the metal layers 26and 28 and the contact pads 16.

The referenced application can be further extended by applying multiplelayers of polymer (such as polyimide) and can therefore be adapted to alarger variety of applications. The function of the structure that hasbeen described in FIG. 6 can be further extended by depositing a secondlayer of polyimide on top of the previously deposited layer 20 andoverlaying the pads 26 and 28. Selective etching and metal deposition orelectro plating of metal can further create additional contact points onthe surface of the second layer of polyimide that can be interconnectedwith pads 26 and 28. Additional layers of polyimide and the thereoncreated contact pads can be customized to a particular application; theindicated extension of multiple layers of polyimides greatly enhancesthe flexibility and usefulness of the referenced application.

FIG. 6 shows a basic design advantage of the referenced application.This advantage allows for the sub-micron or fine-lines that run in theimmediate vicinity of the metal layers 14 and the contact points 16 tobe extended in an upward direction 30 through metal interconnect in theopening 36; this extension continues in the direction 32 in thehorizontal plane of the metal interconnect 28 and comes back down in thedownward direction 34 through metal interconnect in the opening 38. Thefunctions and constructs of the passivation layer 18 and the insulatinglayer 20 remain as previously highlighted. This basic design advantageof the invention is to “elevate” or “fan-out” the fine-lineinterconnects and to remove these interconnects from the micro andsub-micro level to a metal interconnect level that has considerablylarger dimensions and that therefore has smaller resistance andcapacitance and is easier and more cost effective to manufacture. Thisaspect of the referenced application does not include any aspect of padre-distribution and therefore has an inherent quality of simplicity. Ittherefore further adds to the importance of the referenced applicationin that it makes micro and sub-micro wiring accessible at a wide andthick metal level. The interconnections in the openings 22, 36 and 38interconnect the fine-level metal by going up through the passivationand polymer or polyimide dielectric layers 18 and 20, continuing throughthe wide and thick metal level on the polymer layer 20 for a distance,and continuing by descending from the wide and thick metal level backdown to the fine-metal level by again passing down through thepassivation and polymer or polyimide dielectric layers 18 and 20. Theextensions that are in this manner accomplished can extend fine-metalinterconnect points 16 of any particular type, such as signal point orpower point or ground point, to wide and thick metal line 26 and 28. Thelaws of physics and electronics will impose limitations, if any, to theinterconnect established in this manner, and the limiting factors willbe the conventional electrical limiting factors of resistance,propagation delay, RC constants and others. What in the referencedapplication is of importance is that the referenced application providesmuch broader latitude in being able to apply these laws and provides aconsiderably extended scope of the application and use of IntegratedCircuits and the adaptation of these circuits to a wide and thick metalenvironment.

This completes the discussion of the construct shown for purposes ofreference in FIG. 6. Following will further be discussed the crosssections that are shown in FIGS. 7 a and 7 b.

FIG. 7 a shows, for reasons of clarity, a simplified cross section ofthe substrate and the layers that are created on the surface of thesubstrate under the processes of the invention; the highlighted areasthat are shown have previously been identified as:

10 the silicon substrate

12 is a layer of dielectric that has been deposited over the surface ofthe substrate 10

14 is an interconnect layer that contains interconnect lines, vias andcontact points

16 are the contact points on the surface of the interconnect layer 14

18 is a layer of passivation into which openings have been createdthrough which the contact points 16 can be accessed

20 is a thick layer of polymer, and

21 are the conductive plugs that have been provided through the layer 20of polyimide.

The thick layer 20 of polymer can be coated in liquid form on thesurface of the layer 18 of passivation or can be laminated over thesurface of layer 18 of passivation by dry film application. Vias thatare required for the creation of conductive plugs 21 can be defined byconventional processes of photolithography or can be created using laser(drill) technology.

It is clear from previous discussions that the structure of layers thatis shown in cross section in FIG. 7 a has been created so thatadditional electrical components such as an inductor, a capacitor andthe like can be created on the surface of layer 20 of polyimide and inelectrical contact with conductive plugs 21. Layer 12 of dielectric may,in the cross section that is shown in FIG. 7 a, be part of layer 14since layer 14 is a layer of Intra Level Dielectric (ILD) within whichlayer 12 can be readily integrated.

With respect to the cross section that is shown in FIG. 7 b, the samelayers that have been identified for FIG. 7 a are again provided in thiscross section. Additionally has been shown the upper layer 17 of thesilicon substrate 10 that contains active semiconductor devices. Alsoshown is cross section of an inductor 19 that has been created on thesurface of layer 18 of passivation. It must again be emphasized that theohmic resistivity of the metal that is used for the inductor 19 must beas low as possible. For this reason, the use of a thick layer of metal,for instance gold, is preferred for the formation of inductor 19, and ithas been shown that a thick layer of gold, increases the Q value ofinductor 19 from about 5 to about 20 for 2.4 GHz applications, whichrepresents a significant improvement in the Q value of inductor 19.

Referring now specifically to FIG. 3 a, this figure refers only to powerand ground pins and does not address signal or clock pins. There isshown in FIG. 3 a a cross section of a silicon substrate 40 over whichan interconnect network is created according to the invention, with awide and thick wire interconnect network 66 created in a thick layer 64of dielectric overlying a layer 62 of passivation. A power and/or groundpin 68 is provided through the thick layer 64 of dielectric for externalconnection. Following are the various features that are shown in FIG. 3a:

40 is the silicon substrate on the surface of which interconnect linesare created in accordance with the invention

42 are semiconductor circuits that are created in or on the surface ofsubstrate 40

44 is an ESD circuit that is provided for the protection of circuits 42

58 is a layer in which connection pads are created to the semiconductordevices 42 that have been created in or on the surface of substrate 40

60 is a layer of dielectric in which fine-line interconnects have beencreated overlying the layer 58 in which the connection pads 58 arecreated to the semiconductor devices 42

61 is one of the vias that have been provided in layer 60; more suchvias 61 are shown in FIG. 3 a but are, for reasons of simplicity, nothighlighted

62 is a layer of passivation that has been deposited overlying the layer60 of dielectric in which fine-line interconnects are formed

63 is one of vias that passes through layer 62 of passivation; more suchvias 63 are shown in FIG. 3 a but are, for reasons of simplicity, nothighlighted

64 is a layer of dielectric in which, as a post-passivation process,interconnects have been created

65 is a power or ground bus that is connected to the ESD circuit 44,originating in layer 64 and further passing through layers 62 and 60

66 is a power or ground bus providing power or ground (for multipleconnection pads in layer 58)

67 is a via that is created overlying the layer 62 of passivation; moresuch vias 67 are shown in FIG. 3 a but are, for reasons of simplicity,not highlighted

68 is a power or ground pin for the multiple semiconductor devices 42 inlayer 58.

From the cross section that is shown in FIG. 3 a, its is clear that,most importantly, the ability to create interconnects to semiconductordevices 42 that have been created in or on the surface of a substrate 40has been extended by creating these interconnects not only as fine-lineinterconnects in layer 60 but extending the interconnect by creating awide, thick wire interconnect network 66 overlying a layer 62 ofpassivation. This provides immediate and significant benefits in thatthe interconnect network 66 that is created overlying the layer 62 ofpassivation can now contain sturdier, that is thicker and wider,interconnect lines. The thick, wide metal interconnects 66 can be usedfor power and ground distribution, and this distribution 66 takes placeabove a layer 62 of passivation and partially replaces and extends theconventional method of having for these purposes a fine-linedistribution interconnect network in layer 60 under the layer 62 ofpassivation.

Some points of interest can be listed at this time as they relate toprior art methods and to the invention.

Prior Art:

provides an ESD circuit for each pin that is used for externalinput/output interconnect

provides, after ESD stimuli have passed through the ESD circuits, afine-line interconnect network for further distribution of the power andground stimuli, and

the fine-line power and ground distribution network is createdunderneath a layer of passivation.

It must, in this respect and related to the above provided comments, beremembered that power and ground pins do not require drivers and/orreceiver circuitry.

The Invention:

does not need to create an ESD circuit for each pin that is used forexternal input/output interconnect, in view of the more robust wiringthat drives the ESD circuit, resulting in reduced power loss by anunexpected power surge over the interconnect line, resulting in morepower being delivered to the ESD circuit, and

allows for the power and ground interconnects to be directly connectedto the internal circuits of a semiconductor device, either without anESD circuit or with a smaller than regular ESD circuit (as previouslyexplained).

The method that is used to create the interconnect network that is shownin cross section in FIG. 3 a addresses only the use of power and groundconnections and does not apply to clock and signal interconnect lines.FIG. 3 a can be summarized as follows: a silicon substrate 40 isprovided in the surface of which have been created semiconductor devices42 and at least one electrostatic discharge (ESD) circuit 44, a firstlayer 60 of dielectric is deposited over the substrate 40, and afine-line interconnect network 61 is created in the first layer 60 ofdielectric making contact with the active circuits 42 and the ESDcircuit 44. A layer 62 of passivation is deposited over the surface ofthe first layer 60 of dielectric, and a pattern of metal plugs 63 iscreated in the layer 62 of passivation that aligns with points ofcontact created in the surface of the first layer 60 of dielectric. Asecond layer 64 of dielectric is deposited over the surface of the layer62 of passivation, and a wide thick line interconnect network 66 iscreated in said the layer 64 of dielectric, connected to the ESDcircuits 44. A point of electrical contact 68 comprising a power orground contact is provided in the surface of said second layer 64 ofdielectric. The ESD circuit 44 is connected, in parallel with theinternal circuits 42, to an external connection point 68.

FIG. 3 b provides further insight into the creation of the power andground interconnect lines of the invention whereby these interconnectlines have been shown with interconnect lines 66 and interconnect lines66′. Interconnect lines 66 have been created above the layer 62 ofpassivation and act as global power and ground interconnect lines.Interconnect lines 66′ have been created below the layer 62 ofpassivation and act as local power and ground interconnect lines.

Referring now to FIG. 4 a, FIG. 4 a addresses the interconnections ofsignal and clock line. In FIG. 4 a there is shown a cross section of asilicon substrate 40 over which an interconnect network is createdaccording to the invention. An access pin 70 to an ESD circuit 45 ordriver circuits 45′ or receiver circuits 45′ or I/O circuits 45′ isprovided through the surface of the layer 64 of dielectric for externalconnection. The ESD circuit 45 is required for all circuits 42 to whichan I/O connection 70 is established, and the I/O interconnect 70 canalso be provided to a receiver circuit 45′ or a driver circuit 45′ or anI/O circuit 45′.

The features not previously highlighted in FIGS. 3 a and 3 b but shownin FIG. 4 a are:

the invention provides an interconnect network comprising wide, thickinterconnect lines 72 for distribution of the clock and signal stimuli

the invention creates an interconnect network of thick, wideinterconnect lines 72 for the clock and signal stimuli overlying a layer62 of passivation,

70 is an external connection (pin) that is provided for the ESD circuit45 and for driver/receiver/I/O circuit 45′, and pin 70 provides anexternal access for clock and signal stimuli to circuits 45 and 45′, and

72 is a clock or signal bus that is created in the dielectric layer 64using thick, wide wires for interconnect lines; it must be noted thatthe clock and signal interconnect line distribution 72 is entirelycontained within the layer 64 without providing an external point of I/Ointerconnect.

The method that is used to create the interconnect network that is shownin cross section in FIG. 4 a can be summarized as follows. A siliconsubstrate 40 is provided, and active circuits 42, 45 and 45′ have beencreated in the surface of the substrate 40 including an ESD circuit 45,receiver 45′, driver 45′ and I/O circuit 45′. First layers 60 ofdielectric of inorganic material are deposited over the substrate 40,and a fine-line interconnect network 61 is created in the layers 60 ofdielectric, making contact with the active circuitry 42, 45 and 45′. Alayer 62 of passivation is deposited over the first thin layers 60 ofdielectric, a pattern of metal plugs 63 is created in the layer 62 ofpassivation, and the metal interconnects 63 align with points ofelectrical contact in the surface of the first layers 60 of dielectric.One or more thicker layers 64 of dielectric are deposited over thesurface of the layer 62 of passivation, typically of an organicmaterial, and a wide thick line interconnect network 72 is created inthe thicker layer 64 of dielectric, making electrical contact with themetal plugs 63 or the metal pads of the fine-line interconnect network61 in or under the layer 62 of passivation, and connected to thesemiconductor devices 42 and receiver 45′, driver 45′ or I/O circuit45′. A point 70 of electrical contact is provided in the surface of thesecond layer 64 of dielectric and connected to the ESD circuit 45, andreceiver 45′, driver 45′ or I/O circuit 45′. The driver, receiver or I/Ocircuit 45′ is connected in series between the wide thick lineinterconnect network 72 and the external connection point 70. The ESDcircuit 45 is connected, in parallel with the driver, receiver or I/Ocircuit 45′, to the external connection point 70.

FIG. 4 b provides further insight into the creation of the signal andclock interconnect lines of the invention whereby these interconnectlines have been shown with interconnect lines 71 and interconnect lines71′. Interconnect lines 71 have been created above the layer 62 ofpassivation and act as global signal and clock interconnect lines.Interconnect lines 71′ have been created below the layer 62 ofpassivation and act as local signal and clock interconnect lines.

FIG. 5 a shows a cross section of a silicon substrate 40 over which aninterconnect network is created according to the invention, with theinterconnect network 74 created in a thick layer 64 of dielectricoverlying a layer 62 of passivation. No ESD, receiver, driver or I/Ocircuit access pin is provided through the surface of the layer 64 ofdielectric for external connection. Shown in FIG. 5 a and not previouslyhighlighted is the clock or signal interconnect line 74, providing foran interconnect scheme of thick, wide lines overlying a passivationlayer 62 whereby no external I/O connections are provided. Due to thethick, wide lines of the interconnect network 74 that is createdoverlying a passivation layer 62, the clock and signal distribution 74can take place entirely within the layer 64, as opposed to prior artmethods where, for clock and signal distribution lines, each thick, wideinterconnect line (where such thick, wide interconnect lines are used)must be provided with at least one I/O connect point for off-chipconnection.

The method that is used to create the wide thick interconnect lines thatis shown in cross section in FIG. 5 a can be summarized as follows andis similar to that described above for FIG. 4 a. A silicon substrate 40is provided, and active devices 42 have been provided in the surface ofthe substrate 40. First thin layers 60 of dielectric are deposited overthe surface of the substrate 40, and a fine-line interconnect network 61is created in the first layers 60 of dielectric comprising fine-lineinterconnect lines, making contact with points of electrical contact ofthe active devices 42 in the surface of the substrate 42. A layer 62 ofpassivation is deposited over the surface of the first layers 60 ofdielectric, and a pattern of conductive interconnects 63 is created inthe layer 62 of passivation that aligns with the points of electricalcontact of the fine-line interconnect network 61 in the surface of thefirst layer 60 of dielectric. One or more second layers 64 of dielectricare deposited over the surface of the layer 62 of passivation, theinterconnect network 74 in the second layers 64 of dielectric makingelectrical contact with the conductive interconnects 63 in the layer 62of passivation.

FIG. 5 b provides further insight into the creation of the signal andclock interconnect lines of the invention whereby these interconnectlines have been shown with interconnect lines 74 and interconnect lines74′. Interconnect lines 74 have been created above the layer 62 ofpassivation and can act as global signal and clock interconnect lines.Interconnect lines 74′ have been created below the layer 62 ofpassivation and act as local signal and clock interconnect lines.

It must further be emphasized that, where FIGS. 3-5 show a fine-lineinterconnect network in the layer 60 that underlies the layer 62 ofpassivation, the invention also enables and can be further extended withthe complete elimination of the fine-line interconnect network in thelayer 60, however, creating an interconnect network in the layer 64 thatuses only thick, wide wires. For this application of the invention, thefirst layer of dielectric 60 is not applied, and the layer 62 ofpassivation is deposited directly over the surface of the createdsemiconductor devices 42 in or on the surface of substrate 40.

It is further of value to briefly discuss the above implemented andaddressed distinction between fine-line interconnect lines and wide,thick interconnect lines. The following points apply in this respect:

the prior art fine line interconnect lines are created underneath alayer of passivation, the wide, thick interconnect lines of theinvention are created above a layer of passivation

the fine-line interconnect lines are typically created in a layer ofinorganic dielectric, the thick wide interconnect lines are typicallycreated in a layer of dielectric comprising polymer. This is because aninorganic material cannot be deposited as a thick layer of dielectricbecause such a layer of dielectric would develop fissures and crack as aresult

fine-line interconnect metal is typically created using methods ofsputter with resist etching or of damascene processes using oxide etchwith electroplating after which CMP is applied. Either one of these twoapproaches cannot create thick metal due to cost considerations or oxidecracking

thick, wide interconnect lines can be created by first sputtering a thinmetal base layer, coating and patterning a thick layer of photoresist,applying a thick layer of metal by electroplating, removing thepatterned thick layer of photoresist and performing metal base etching(of the sputtered thin metal base layer). This method allows for thecreation of a pattern of very thick metal, and metal thickness in excessof 1 μm can in this manner be achieved while the thickness of the layerof dielectric in which the thick metal interconnect lines are createdcan be in excess of 2 μm.

Although the invention has been described and illustrated with referenceto specific illustrative embodiments thereof, it is not intended thatthe invention be limited to those illustrative embodiments. Thoseskilled in the art will recognize that variations and modifications canbe made without departing from the spirit of the invention. It istherefore intended to include within the invention all such variationsand modifications which fall within the scope of the appended claims andequivalents thereof.

What is claimed is:
 1. A method for fabricating a chip, comprising:providing a silicon substrate and an interconnecting structure over saidsilicon substrate, wherein said interconnecting structure is formed by aprocess comprising a damascene process, an electroplating process and aCMP process; and forming a power bus over said silicon substrate,wherein said forming said power bus comprises forming a first metallayer, followed by forming a patterned photoresist layer, followed byelectroplating a second metal layer, followed by removing said patternedphotoresist layer, followed by etching said first metal layer.
 2. Themethod of claim 1, wherein said forming said first metal layer comprisesa sputtering process.
 3. The method of claim 1 further comprisingproviding an internal circuit in or on said silicon substrate, whereinsaid power bus is connected to said internal circuit through saidinterconnecting structure.
 4. The method of claim 1 further comprisingproviding an ESD circuit in or on said silicon substrate, wherein saidpower bus is connected to said ESD circuit through said interconnectingstructure.
 5. The method of claim 1 further comprising providing adielectric layer over said silicon substrate, wherein saidinterconnecting structure is in said dielectric layer, and a passivationlayer over said dielectric layer, wherein said passivation layercomprises a nitride layer, wherein said forming said power bus comprisessaid forming said power bus further over said passivation layer.
 6. Themethod of claim 5 further comprising providing a polymer layer over saidpassivation layer, wherein said polymer layer comprises a portion oversaid power bus.
 7. The method of claim 6, wherein said polymer layer hasa thickness greater than 2 micrometers.
 8. The method of claim 1,wherein said power bus has a thickness greater than 1 micrometer.
 9. Amethod for fabricating a chip, comprising: providing a siliconsubstrate, a first internal circuit in or on said silicon substrate, asecond internal circuit in or on said silicon substrate, a dielectriclayer over said silicon substrate, a first interconnecting structureover said silicon substrate and in said dielectric layer, wherein saidfirst interconnecting structure is connected to said first internalcircuit, a second interconnecting structure over said silicon substrateand in said dielectric layer, wherein said second interconnectingstructure is connected to said second internal circuit, and apassivation layer over said dielectric layer; and forming a power busand a polymer layer over said passivation layer, wherein said polymerlayer comprises a portion over said power bus, wherein said firstinternal circuit is connected to said second internal circuit through,in sequence, said first interconnecting structure, said power bus andsaid second interconnecting structure, wherein said forming said powerbus comprises forming a first metal layer, followed by forming apatterned photoresist layer, followed by electroplating a second metallayer, followed by removing said patterned photoresist layer, followedby etching said first metal layer.
 10. The method of claim 9, whereinsaid forming said first metal layer comprises a sputtering process. 11.The method of claim 9, wherein said first and second interconnectingstructures are formed by a process comprising a damascene process, anelectroplating process and a CMP process.
 12. The method of claim 9,wherein said first and second interconnecting structures are formed by aprocess comprising a sputtering process and an etching process.
 13. Themethod of claim 9, wherein said polymer layer has a thickness greaterthan 2 micrometers.
 14. The method of claim 9, wherein said power bushas a thickness greater than 1 micrometer.
 15. The method of claim 9,wherein said passivation layer comprises a nitride layer and an oxidelayer.
 16. The method of claim 9, wherein said passivation layercomprises a nitride layer.
 17. A method for fabricating a chip,comprising: providing a silicon substrate, a dielectric layer over saidsilicon substrate, an interconnecting structure over said siliconsubstrate and in said dielectric layer, and a separating layer over saiddielectric layer, wherein said interconnecting structure is formed by aprocess comprising a damascene process, an electroplating process and aCMP process, wherein said separating layer comprises an oxide layer; andforming an interconnect line over said separating layer, wherein saidinterconnect line is connected to said interconnecting structure througha via in said separating layer, wherein said forming said interconnectline comprises forming a first metal layer, followed by forming apatterned photoresist layer, followed by electroplating a second metallayer, followed by removing said patterned photoresist layer, followedby etching said first metal layer.
 18. The method of claim 17, whereinsaid forming said first metal layer comprises a sputtering process. 19.The method of claim 17 further comprising providing an internal circuitin or on said silicon substrate.
 20. The method of claim 17 furthercomprising providing an ESD circuit in or on said silicon substrate. 21.The method of claim 17 further comprising providing a polymer layer oversaid separating layer, wherein said polymer layer has a portion oversaid interconnect line.
 22. The method of claim 21, wherein said polymerlayer has a thickness greater that 2 micrometers.
 23. The method ofclaim 17, wherein said interconnect line has a thickness greater than 1micrometer.
 24. A method for fabricating a chip, comprising: providing asilicon substrate, a dielectric layer over said silicon substrate, afirst interconnecting structure over said silicon substrate and in saiddielectric layer, a second interconnecting structure over said siliconsubstrate and in said dielectric layer, wherein said first and secondinterconnecting structures are formed by a process comprising adamascene process, an electroplating process and a CMP process, and aseparating layer over said dielectric layer, wherein said separatinglayer comprises a nitride; and forming a power interconnect and apolymer layer over said separating layer, wherein said polymer layer hasa portion over said power interconnect, wherein said firstinterconnecting structure is connected to said second interconnectingstructure through said power interconnect, wherein said forming saidpower interconnect comprises forming a first metal layer, followed byforming a patterned photoresist layer, followed by electroplating asecond metal layer, followed by removing said patterned photoresistlayer, followed by etching said first metal layer.
 25. The method ofclaim 24, wherein said forming said first metal layer comprises asputtering process.
 26. The method of claim 24 further comprisingproviding an internal circuit in or on said silicon substrate.
 27. Themethod of claim 24 further comprising providing an ESD circuit in or onsaid silicon substrate.
 28. A method for fabricating a chip, comprising:providing a silicon substrate, a dielectric layer over said siliconsubstrate, a first interconnecting structure over said silicon substrateand in said dielectric layer, wherein said first interconnectingstructure is formed by a process comprising a damascene process, anelectroplating process and a CMP process, a second interconnectingstructure over said silicon substrate and in said dielectric layer, anda separating layer over said dielectric layer; and forming a signalinterconnect over said separating layer, wherein said firstinterconnecting structure is connected to said second interconnectingstructure through said signal interconnect, wherein a top surface ofsaid signal interconnect has no access for external connection, whereinsaid forming said signal interconnect comprises forming a first metallayer, followed by forming a patterned photoresist layer, followed byelectroplating a second metal layer, followed by removing said patternedphotoresist layer, followed by etching said first metal layer.
 29. Themethod of claim 28, wherein said forming said first metal layercomprises a sputtering process.
 30. The method of claim 28 furthercomprising providing a polymer layer over said separating layer, whereinsaid polymer layer comprises a portion over said signal interconnect.